CVE-2025-61100 is a vulnerability identified in the FRRouting (FRR) software suite, specifically affecting versions from 2.0 up to 10.4.1. The flaw resides in the ospf_opaque_lsa_dump function within the ospf_opaque.c source file, where a NULL pointer dereference can occur when processing certain malformed OSPF (Open Shortest Path First) Link State Advertisements (LSAs). This vulnerability can be triggered by an attacker crafting and sending specially malformed OSPF opaque LSAs to the FRR daemon. When these malformed LSAs are processed, the NULL pointer dereference leads to a crash of the FRR process, resulting in a denial of service (DoS) condition. This disrupts the routing functionality provided by FRR, potentially causing network outages or degraded performance. The vulnerability does not require authentication, but exploitation requires the ability to inject or relay OSPF packets into the network segment where FRR is operating, which typically means the attacker must have some level of network access or control over a compromised device within the routing domain. No CVSS score has been assigned yet, and no public exploits are known at this time. The absence of patches or mitigation details suggests that vendors and users should prioritize monitoring and prepare for updates. FRR is widely used in service provider networks, data centers, and enterprise environments for dynamic routing, making this vulnerability significant for critical infrastructure. The nature of the vulnerability—causing a crash via malformed routing protocol messages—means it can be weaponized to disrupt network availability without compromising confidentiality or integrity directly.

For European organizations, the impact of CVE-2025-61100 can be substantial, especially for those relying on FRRouting for OSPF-based routing in their core or edge network infrastructure. A successful exploit leads to denial of service by crashing the routing daemon, which can cause network outages, routing instability, and loss of connectivity for critical services. This can affect internet service providers, cloud providers, large enterprises, and data centers that depend on FRR for dynamic routing. Disruptions in routing can cascade, affecting multiple dependent systems and services, potentially impacting business continuity and operational capabilities. Given the reliance on OSPF in many European telecom and enterprise networks, the vulnerability poses a risk to network availability and service reliability. While the vulnerability does not appear to allow remote code execution or data compromise, the availability impact alone can be severe, especially in high-availability environments. The lack of known exploits reduces immediate risk but also means organizations should proactively prepare defenses. The threat is more pronounced in environments where network segmentation is weak, allowing attackers to inject malicious OSPF packets.

To mitigate CVE-2025-61100, European organizations should implement several specific measures beyond generic advice: 1) Network segmentation and strict access controls should be enforced to limit which devices can send OSPF packets to FRR routers, reducing the attack surface. 2) Deploy OSPF authentication mechanisms (e.g., MD5 or SHA-based authentication) to ensure only authorized routers can participate in OSPF exchanges, preventing unauthorized LSA injection. 3) Monitor OSPF traffic for anomalies such as malformed LSAs or unexpected opaque LSAs using network intrusion detection systems (NIDS) or specialized routing protocol monitoring tools. 4) Prepare for rapid patch deployment by tracking vendor advisories and subscribing to FRR security mailing lists, as patches are expected to be released following disclosure. 5) Consider implementing rate limiting or filtering on OSPF packets at network boundaries to reduce the risk of malformed packet floods. 6) Conduct regular network device and routing daemon health checks to detect crashes or restarts promptly. 7) In virtualized or containerized environments, isolate routing processes to minimize impact scope. These targeted mitigations will help reduce the likelihood and impact of exploitation until patches are available.